Drugs are most commonly administered orally and as such must be placed in a suitable form for oral ingestion. Not only must the drug be adapted to be delivered at desirable dosage levels but, at times, depending upon the nature of the drug, must be protected from rapid moisture absorption.
Certain hygroscopic drugs have distinctly unpleasant tastes and odors. In addition hygroscopic and waxy drugs present processing problems during tabletting and encapsulation. Examples of drugs which possess one or more of these properties are oxtriphylline, procainamide HCl, gemfibrozil, disopyramide phosphate, fenoprofen calcium, atenolol, piracetam, carbamazepine, tetracycline HCl, oxytetracycline HCl, rifamprin, lincomycin HCl, clindamycin HCl, cefaclor, cefadroxil, cephrabine, thiamine HCl, ascorbic acid, acetysalicylic acid, methocarbamol, methyldopa, sulindac, desipramine HCl, ranitine HCl, ethionamide, divalproex sodium, meprobamate, captopril, and aminophylline. These drugs as well as other hygroscopic unpleasant tasting drugs are known for purposes of this specification as malflavored drugs and, because of their off flavors and difficult handling, provide problems both for the drug manufacturer as well as in the area of patient compliance in taking proper amounts.
Silicon dioxide is an ingredient commonly used in the tablet art as an aid to tablet processing. Low levels of silicon dioxide usually below 2% are generally employed. European Patent Application 108,218 by James Michael Dunn et al describes the formation of constant release rate tablets of water soluble drugs employing from 0.5 to 3 rate percent of fumed silicon dioxide as a lubricant.
U.S. Pat. No. 4,536,511 issued to Wolfgang Fisher et al, discloses a drug specific combination including levels of silica and cellulose below 1% evidently to aid binding and flow characteristics in a wet granulation system for the drug muzolimine.
U.S. Pat. No. 4,526,777 issued to Cheryl D. Blume et al discloses the combination of two dry granulations including microcrystalline cellulose as a binding and disintergrant with syloid as a flow enhancer again in precedingly low levels.
Patents issued to James M. Dunn, namely U.S. Nos. 4,461,759; 4,522,804; 4,521,402; and 4,521,401 disclose 0.4 to 3.09% silicon dioxide in combination with hydrogenated vegetable oil and an acrylic acid polymer.
U.S. Pat. No. 4,609,675 issued to Robert M. Franz discloses using silicon dioxide at a 1% level for dry granulation of ibuprofen.
U.S. Pat. No. 4,478,819 issued to Hercelin, teaches silicon dioxide used in forming extruded granules. U.S. Pat. No. 4,442,086 issued to James M. Quinlan discloses the use of silica as a glidant at levels not greater than 0.05%.
U.S. Pat. No. 4,415,547 teaches the use of silica dioxide as a dusting powder for pellets which are subsequently compressed into tablets.
U.S. Pat. No. 3,592,927 issued to Maximillan Koffier discloses a calcium pantothenate composition which is produced in dry free flowing form by the inclusion of silicon dioxide during its manufacturer at a level below 5%.
In addition, European Patent Application 167,191 discloses the inclusion of silicon dioxide as an aid to direct compression of tablets. European Patent Application 136,100 discloses the combination of sucralfate with microcrystalline cellulose and colloidal silicon dioxide as a suspending agent at extremely low levels.